Ishizuchi Kanamono Manufactory
I still remember one of my earliest experiences with a Japanese knife burr.
I had only recently started working as a chef, and like every young cook, I was learning how to sharpen my own knives. One day, while sharpening, a tiny piece of metal suddenly came off the edge.
I looked at it and genuinely thought part of my knife blade had broken away.
So I went to the head chef and said something like, “Chef, part of the blade just came off. Is this okay?”
I can still remember his face.
He looked at me as if he was thinking, What on earth is this guy talking about?
Looking back now, it makes me laugh.
The blade had not fallen off at all.
What I had seen was a Japanese knife burr coming away from the edge.
After more than 25 years working as a chef in Japan and Australia, I have sharpened countless knives since then. But recently I realised something: although I had learned to recognise a burr through experience, I had never really stopped to investigate what it actually is.
So, once again, I decided to look into it.
What Is a Japanese Knife Burr?
When sharpening a knife on a whetstone, we are removing a very small amount of steel from the blade. As the abrasive surface of the stone works against the steel, the geometry of the edge gradually changes until the sharpening reaches the very apex.
At that point, extremely thin metal at the edge can be pushed over to the opposite side. This thin, folded-over material is what we commonly call a burr.
In Japanese sharpening, it is often referred to as kaeri (返り), or ha-gaeri (刃返り).
That tiny piece of metal I saw as a young chef was therefore not my knife mysteriously losing its cutting edge. It was material created during the sharpening process.
If somebody had explained that to me at the time, I probably would not have asked my head chef whether my blade had fallen off.
But making mistakes is often how we remember things.
👉 INTERNAL LINK: Read “Whetstone Flattening” here
Why Does a Japanese Knife Burr Appear?
A Japanese knife burr can be useful because it gives us information about what is happening at the edge.
If you sharpen one side and eventually detect a burr along the opposite side, it generally indicates that your sharpening has reached the apex in that area.
But there is an important distinction.
Creating a huge burr is not the goal of sharpening.
When I was younger, I sometimes thought that if I could clearly feel a large burr, I must have sharpened the knife properly. With experience, I learned that continuing to grind away steel simply to make a larger burr is unnecessary.
You are removing steel every time you sharpen.
The purpose is to create a clean, properly formed cutting edge—not to remove as much metal as possible.
👉 INTERNAL LINK: Read “How to Sharpen Japanese Knives” here
A Bigger Japanese Knife Burr Is Not Necessarily Better
This is where sharpening becomes more interesting.
A large Japanese knife burr may actually be a sign that you have continued sharpening longer than necessary. Once the abrasive has reached the apex and a burr has formed, repeatedly grinding the same side can simply produce more deformation and remove more steel.
This connects with something I have learned through my own mistakes.
If you keep sharpening at too high an angle, the geometry around the cutting edge can gradually become thicker. Similarly, using a whetstone that is no longer flat can affect the geometry you are trying to create.
Sharpening is not only about making a knife feel sharp today. It is also about maintaining the blade over many years.
👉 INTERNAL LINK: Read “Japanese Knife Bevels | Single vs Double” here
Removing the Japanese Knife Burr Matters Too
Forming the burr is only part of the process.
Eventually, that weakened metal needs to be removed cleanly.
Simply leaving a large burr attached can create the impression of an extremely sharp knife at first, but that fragile metal may fold, break away or disappear quickly during use.
This is one reason the finishing stages of sharpening matter.
I normally use a 1000-grit stone for my main sharpening and then move to a 6000-grit stone for finishing. The lighter work at the end is not about aggressively removing more steel. I am refining the edge and reducing what remains of the burr.
The more knives I sharpen, the more I feel that the final light touches are just as important as the earlier grinding.
👉 INTERNAL LINK: Read “The True Value of Japanese Knives” here
Japanese Knife Burrs Taught Me Something About Sharpening
There is another lesson hidden in that embarrassing story from when I first became a chef.
Nobody starts out knowing how to sharpen.
You can read about angles, steels, whetstones and edge geometry, but eventually you have to put a knife on a stone and learn what is happening through your hands.
Over the years I have used carbon steels, stainless steels and modern high-performance steels, and they do not always feel exactly the same on a whetstone.
That tactile experience is one of the things I still find fascinating about Japanese knives.
👉 INTERNAL LINK: Read “Kireaji — What Does Sharpness Really Feel Like?” here
The Japanese Knife Burr Is a Sign, Not the Goal
More than 25 years after telling my head chef that “the blade came off,” I can finally give my younger self a better answer.
Don’t worry.
The blade didn’t fall off.
It was just the burr.
A Japanese knife burr is useful because it can tell us that sharpening has reached the edge, but producing the biggest possible burr does not mean producing the best possible edge.
For me, that is the real conclusion.
The burr is a sign during sharpening. It is not the goal of sharpening.
And perhaps that is why I still remember that confused look on my head chef’s face all these years later.
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Thank you for reading, and I hope to see you again in the next story.
